Carbenes cycloalkyl

Alkyl(silyl)carbenes and cycloalkyl(silyl)carbenes. 743... 

Cycloalkyl(silyl)carbenes with an a-C—H bond have not yet been investigated systematically. When cyclohexyl(trimethylsilyl)carbene was generated by thermal a-elimination from cyclohexyl-bis(trimethylsilyl)methanol at 500 °C, only the (1,2) hydride shift took place, whereas cyclopentyl(trimethylsilyl)carbene, generated analogously, gave both the endocyclic alkene and the 1,3-C,H insertion product85,86 (equation 47). 

Generation of Alkyl and Cycloalkyl Carbenes - Photolysis or thermolysis of a series of alkylchlorodiazirines (16) (Scheme 7) in the presence of alkenes, such as tetramethylethene, results in 1,2-H shifts, giving the corresponding vinyl chorides (18), in competition with additions of the carbenes (17) to the alkenes, yielding cyclopropanes (19). The mechanism of these reactions is discussed in the light of results obtained from photoacoustic calorimetry, and the ratio of vinyl chloride to cyclopropane seems to depend on the excited states of the carbene precursors and also on carbene-alkene complexes. Similar reactions of related diazirines have been investigated by flash photolysis. 

Chloro(cycloalkyl)carbenes (or carbenoids) undergo addition to alkenes to give 1-chloro-l-cycloalkylcyclopropanes. Two methods for the synthesis of these products are known ... 

The photolysis or thermolysis of 3-chloro-3-cyclobutyl- and 3-chloro-3-cyclopropyl-3/7-diazirine " generates chloro(cycloalkyl)carbenes which react with alkenes to form 1-chloro-l-cyclobutyl- or 1-chloro-l-cyclopropylcyclopropanes 1 and 2, respectively (Houben-Weyl, Vol. E19b, pp 1520-1521). 

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